Especially when electronic services become more common, a need has arisen to verify the transaction time of the electronic services. Systems have been developed for this purpose, in which time data is maintained and certified time data is transmitted to a terminal in which the time data is used for generating a time stamp of the events. Furthermore, this time data can be used for setting the real-time clock of the terminal itself to a time indicated by the time data. A problem in such a system is that the time data can be transmitted to the terminal only when the terminal is connected to such a communication network via which time data can be transmitted. In a situation in which the terminal is not connected to this communication network, time data is typically maintained by means of the real-time clock of the terminal itself. However, such a real-time clock of a terminal is not necessarily very accurate, wherein the time data in the real-time clock of the terminal is inaccurate already within a relatively short period of time. Moreover, the user may, if he/she so desires, change the time data in the real-time clock of the terminal, wherein the user can set the time data so that it is inaccurate and advantageous for the user himself/herself. Thus, the user may try to correct his/her own neglect by distorting the time for example in a situation where an electronic event should have been performed by a fixed term. Such a situation may occur for example when the user sends his/her tax return electronically, or a facsimile, an e-mail or any other electronic document after a deadline. Furthermore, by changing the time data in the real-time clock of the terminal the user may attempt to obtain more operating time for example for such programs which have a limited operating time, or for example when a limited usage time is set for a piece of music retrieved from a communication network to the terminal.